diff --git a/core/includes/form.inc b/core/includes/form.inc
index bd256ad..561e042 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -18,14 +18,15 @@
  * Default template: select.html.twig.
  *
  * It is possible to group options together; to do this, change the format of
- * $options to an associative array in which the keys are group labels, and the
- * values are associative arrays in the normal $options format.
+ * the #options property to an associative array in which the keys are group
+ * labels, and the values are associative arrays in the normal #options format.
  *
  * @param $variables
  *   An associative array containing:
  *   - element: An associative array containing the properties of the element.
  *     Properties used: #title, #value, #options, #description, #extra,
- *     #multiple, #required, #name, #attributes, #size.
+ *     #multiple, #required, #name, #attributes, #size, #sort_options,
+ *     #sort_start.
  */
 function template_preprocess_select(&$variables) {
   $element = $variables['element'];
@@ -37,7 +38,7 @@ function template_preprocess_select(&$variables) {
 }
 
 /**
- * Converts an options form element into a structured array for output.
+ * Converts the options in a select element into a structured array for output.
  *
  * This function calls itself recursively to obtain the values for each optgroup
  * within the list of options and when the function encounters an object with
@@ -63,6 +64,12 @@ function template_preprocess_select(&$variables) {
  *       object with an 'option' property, the key is ignored, the contents of
  *       the option property are interpreted as $element['#options'], and the
  *       resulting HTML is added to the output.
+ *   - #sort_options: (optional) If set to TRUE (default is FALSE), sort the
+ *     options by their labels. Can be set within an option group to sort that
+ *     group.
+ *   - #sort_start: (optional) Option index to start sorting at, where 0 is the
+ *     first option (default is 0, and this only applies if #sort_options is
+ *     TRUE). Can be used within an option group.
  *   - #value: Optional integer, string, or array representing which option(s)
  *     to pre-select when the list is first displayed. The integer or string
  *     must match the key of an option in the '#options' list. If '#multiple' is
@@ -90,7 +97,17 @@ function form_select_options($element, $choices = NULL) {
       return [];
     }
     $choices = $element['#options'];
+    $sort_options = isset($element['#sort_options']) && $element['#sort_options'];
+    $sort_start = (isset($element['#sort_start']) ? $element['#sort_start'] : 0);
   }
+  else {
+    // We are within an option group.
+    $sort_options = isset($choices['#sort_options']) && $choices['#sort_options'];
+    $sort_start = (isset($choices['#sort_start']) ? $choices['#sort_start'] : 0);
+    unset($choices['#sort_options']);
+    unset($choices['#sort_start']);
+  }
+
   // array_key_exists() accommodates the rare event where $element['#value'] is NULL.
   // isset() fails in this situation.
   $value_valid = isset($element['#value']) || array_key_exists('#value', $element);
@@ -125,6 +142,16 @@ function form_select_options($element, $choices = NULL) {
       $options[] = $option;
     }
   }
+  if ($sort_options) {
+    $unsorted = array_slice($options, 0, $sort_start);
+    $sorted = array_slice($options, $sort_start);
+    uasort($sorted, function ($a, $b) {
+        $label1 = (string) $a['label'];
+        $label2 = (string) $b['label'];
+        return strcmp($label1, $label2);
+    });
+    $options = array_merge($unsorted, $sorted);
+  }
   return $options;
 }
 
diff --git a/core/lib/Drupal/Core/Render/Element/Select.php b/core/lib/Drupal/Core/Render/Element/Select.php
index 300c244..908ea43 100644
--- a/core/lib/Drupal/Core/Render/Element/Select.php
+++ b/core/lib/Drupal/Core/Render/Element/Select.php
@@ -14,6 +14,12 @@
  *   list. If a value is an array, it will be rendered similarly, but as an
  *   optgroup. The key of the sub-array will be used as the label for the
  *   optgroup. Nesting optgroups is not allowed.
+ * - #sort_options: (optional) If set to TRUE (default is FALSE), sort the
+ *   options by their labels, after rendering and translation is complete.
+ *   Can be set within an option group to sort that group.
+ * - #sort_start: (optional) Option index to start sorting at, where 0 is the
+ *   first option (default is 0, and this only applies if #sort_options is
+ *   TRUE). Can be used within an option group.
  * - #empty_option: (optional) The label to show for the first default option.
  *   By default, the label is automatically set to "- Select -" for a required
  *   field and "- None -" for an optional field.
@@ -68,6 +74,8 @@ public function getInfo() {
     return [
       '#input' => TRUE,
       '#multiple' => FALSE,
+      '#sort_options' => FALSE,
+      '#sort_start' => 0,
       '#process' => [
         [$class, 'processSelect'],
         [$class, 'processAjaxForm'],
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php
index d1b14d8..9f2d7e6 100644
--- a/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php
@@ -4,6 +4,7 @@
 
 use Drupal\Core\Form\FormBase;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
 use Symfony\Component\HttpFoundation\JsonResponse;
 
 /**
@@ -125,6 +126,61 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       ],
     ];
 
+    $unsorted_options = [
+      // Don't use $this->t() here, because we really don't want these
+      // to be translated or added to localize.d.o. Using TranslatableMarkup
+      // in places tests that casting to string is working, however.
+      'uso_none' => new TranslatableMarkup('- none -'),
+      'uso_second' => new TranslatableMarkup('second element'),
+      'uso_zzgroup' => [
+        'uso_gc' => new TranslatableMarkup('group c'),
+        'uso_ga' => new TranslatableMarkup('group a'),
+        'uso_gb' => 'group b',
+      ],
+      'uso_yygroup' => [
+        'uso_ge' => new TranslatableMarkup('group e'),
+        'uso_gd' => new TranslatableMarkup('group d'),
+        'uso_gf' => new TranslatableMarkup('group f'),
+      ],
+      'uso_d' => 'd',
+      'uso_c' => new TranslatableMarkup('main c'),
+      'uso_b' => new TranslatableMarkup('main b'),
+      'uso_a' => 'a',
+    ];
+
+    $form['unsorted'] = [
+      '#type' => 'select',
+      '#options' => $unsorted_options,
+    ];
+
+    // For the sorted select element, replace 'uso' in the keys with 'sso' so
+    // keys are all unique between the sorted and unsorted select, for testing.
+    $sortable_options = [];
+    foreach ($unsorted_options as $key => $item) {
+      $key = str_replace('uso', 'sso', $key);
+      if (is_array($item)) {
+        $new_item = [];
+        foreach ($item as $subkey => $subitem) {
+          $subkey = str_replace('uso', 'sso', $subkey);
+          $new_item[$subkey] = $subitem;
+        }
+        $sortable_options[$key] = $new_item;
+      }
+      else {
+        $sortable_options[$key] = $item;
+      }
+    }
+
+    // Make the first group sorted, the second group unsorted, and the
+    // sorting on the main list start at element 3.
+    $sortable_options['sso_zzgroup']['#sort_options'] = TRUE;
+    $form['sorted'] = [
+      '#type' => 'select',
+      '#options' => $sortable_options,
+      '#sort_options' => TRUE,
+      '#sort_start' => 3,
+    ];
+
     $form['submit'] = ['#type' => 'submit', '#value' => 'Submit'];
     return $form;
   }
diff --git a/core/modules/system/tests/src/Functional/Form/FormTest.php b/core/modules/system/tests/src/Functional/Form/FormTest.php
index 849944b..6156119 100644
--- a/core/modules/system/tests/src/Functional/Form/FormTest.php
+++ b/core/modules/system/tests/src/Functional/Form/FormTest.php
@@ -464,6 +464,58 @@ public function testEmptySelect() {
   }
 
   /**
+   * Tests sorting and not sorting of options in a select element.
+   */
+  public function testSelectSorting() {
+    $this->drupalGet('form-test/select');
+    $content = $this->getSession()->getPage()->getContent();
+
+    // Verify the expected order of the options in the unsorted and
+    // sorted elements.
+    $expected_order = [
+      'uso_none',
+      'uso_second',
+      'uso_zzgroup',
+      'uso_gc',
+      'uso_ga',
+      'uso_gb',
+      'uso_yygroup',
+      'uso_ge',
+      'uso_gd',
+      'uso_gf',
+      'uso_d',
+      'uso_c',
+      'uso_b',
+      'uso_a',
+      'sso_none',
+      'sso_second',
+      'sso_zzgroup',
+      'sso_ga',
+      'sso_gb',
+      'sso_gc',
+      'sso_a',
+      'sso_d',
+      'sso_b',
+      'sso_c',
+      'sso_yygroup',
+      'sso_ge',
+      'sso_gd',
+      'sso_gf',
+    ];
+
+    $prev_position = 0;
+    foreach ($expected_order as $string) {
+      $position = strpos($content, $string);
+      $this->assertTrue($position > $prev_position, 'Item ' . $string . ' is in correct order');
+      $prev_position = $position;
+    }
+
+    // Verify that #sort_order and #sort_start are not in the page.
+    $this->assertFalse(strpos($content, '#sort_order'), 'Sort order property has been removed');
+    $this->assertFalse(strpos($content, '#sort_start'), 'Sort start property has been removed');
+  }
+
+  /**
    * Tests validation of #type 'number' and 'range' elements.
    */
   public function testNumber() {